(a) Field of the Invention
The present invention relates to a refrigerator that supercools food and stores the supercooled food. More particularly, the present invention relates to a supercooling refrigerator and a method for controlling the same, which easily control a temperature.
(b) Description of the Related Art
In general, food including fish or meat is stored by using a refrigerating device. The refrigerating device is a device for long-term storage of stored goods by decreasing a temperature in an airtight storage chamber to a temperature lower than an external temperature. The refrigerating device includes a refrigeration cycle in which refrigerant is circulated to refrigerate the stored goods through cool air generated while absorbing ambient heat when a refrigerant in a liquid state is evaporated.
The refrigerating device cooling-controls the temperature of the storage chamber storing the food to a temperature below freezing to refrigerate the food. When the food such as the meat or the fish is refrigerated and kept at a low temperature as described above, water included in the food is frozen. Therefore, while the water is frozen, the volume of the food increases and cells are destroyed or only water in the cell is first frozen and water is extricated from tissue, and as a result, an ice crystal is separately generated. Therefore, when the refrigerated food is defrosted, the food is deformed from an original state to lose flavor thereof.
Further, a difference in temperature between the surface and the center of the food stored in a storage chamber becomes large, and as a result, freezing speeds of the surface and the center of the food are different from each other. Therefore, since an ice crystal is formed to grow from the surface to the center of the food, cell destruction of the food increases toward the center of the food.
Further, a phenomenon continuously occurs in which while water at the center of the food is phase-transited to ice, a temperature increases to a freezing point again. Therefore, a period in which a temperature at the center of the food decreases is lengthened, and as a result, the temperature stays long hours in a maximum ice crystal generation zone to generate large ice crystals or needle-shaped ice crystals. The generated ice crystals destroy the cells of the food to degrade quality thereof. As a result, the food, in particular, the food such as the meat or the fish, frequently drips after defrosting and nutrients escape. Therefore, the taste of the food deteriorates.
A technology is presented which supercools stored goods by controlling the temperature of the storage chamber by using supercooling in order to solve the problem.
The supercooling is a phenomenon in which, although a melted object or a solid object is cooled to a phase-transition temperature or lower in a balance state, the melted object or solid object is not changed. Since a material has a stable state depending on the temperature at the time, when the temperature is gradually changed, constituent atoms of the material may correspondingly follow a change in temperature while maintaining the stable state at each temperature. However, when the temperature is unexpectedly changed, since the constituent atoms have no spare time to be changed to the stable state depending on each temperature, the constituent atoms just maintain a stable state at a start-point temperature or some of the constituent atoms stop to not be changed to a state at an end-point temperature.
For example, when water is gradually cooled, the water is not temporarily solidified even though the temperature of the water becomes a temperature of 0° C. or lower. However, when an object is supercooled, the object enters a kind of semi-stable state, and as a result, an unstable balance state is broken even by minor stimulation, and as a result, the state of the object is easily transited to a more stable state. That is, when small pieces of the material are input to a supercooled liquid or the liquid is unexpectedly shaken, the liquid starts to solidify immediately, and as a result, the temperature of the liquid increases up to a solid point and the liquid maintains the stable balance state at the temperature.
A temperature condition should be well adjusted and the adjusted temperature condition should be continuously maintained in order to supercool the foods. However, cooling devices in the related art have difficulty in controlling the temperature of the storage chamber according to a supercooling temperature condition of the food, and in particular, it is very difficult to uniformly maintain a temperature distribution in the storage chamber, and a solution therefor is required.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.